Thailand

Title of the survey

Wages, Earnings and Hours of Work Survey

Organization responsible

Department of Labour Protection and Welfare, Labour Studies and Planning Division.

Periodicity of the survey

Annual, in March.

Objectives of the survey

To obtain data on wage rates, earnings and hours of work by industry and occupation. The survey results are used by wage policy makers, labour administrators and economic and social development planners.

Main labour topics covered by the survey

Employment, earnings, wage rates and hours of work.

Reference period

For employment: 31 March of each year. For wage rates: a normal pay period in March. For other components of earnings: the month of March and the whole preceding year. For hours of work: a week in March.

Coverage of the survey

Geographical

The whole country.

Industrial

All branches of economic activity, except agriculture, hunting, forestry and fishing, and public administration.

Establishments

All types of establishments with one or more employees.

Persons

Employees, excluding home workers, domestic services and unpaid family and other workers.

Occupations

The survey collects data on the "position, task or occupation", of each individual employee in the sampled establishments.

Concepts and definitions

Employment

An employee is defined as a person agreeing to work for an employer in return for wages. Employees include working directors, wage earners and salaried employees, regular and temporary workers and piece workers. Employment data refer to the number of employees on payroll on the 31th of March of each year. Three categories of employees are separately identified:

daily-paid employees,
monthly-paid employees, and
employees on piece work.

Excluded from the number of employees, or not relevant to the survey, are apprentices, trainees and workers on probation, commission agents, and persons absent from payroll during the reference period.

Earnings

Data are collected on gross earnings paid out to each individual employee during the reference month, before deduction of employee's income or other taxes. Gross earnings are defined as the wages which an employee receives, including overtime payments, money or items given by the employer for the purpose of providing assistance or welfare to the employee, e.g. cost-of-living allowance, bonus, meals, accommodation, clothes and travel allowance, and remuneration for time not worked (rest days, annual leave or vacation, etc.). The following components are separately identified:

basic wages (either daily, monthly or piece rates)
overtime payments
cost-of-living allowances paid out during the reference month,
bonuses paid out during the preceding year,
other benefits paid out during the preceding year:
- food (meals per day or baht per month)
- housing (in baht per month)
- clothing (suits per year or baht per month)
- transport (in baht per month)
- other benefits (in baht per month)

Wage/salary rates

For each employee, data are collected on daily, monthly or piece rates, as part of the components of gross earnings (see above). Published statistics of wages refer to average wage rates for normal/usual working hours and working days.

Hours of work

Data are collected on the average number of normal/usual working hours per day of all employees in the sampled establishment; as well as on the number of usual working days per week. Normal/usual working hours refer to the hours of work fixed by the establishment so as to be in accordance with the Labour Protection Law which prescribes that the normal working hours for employees shall be not more than 48 to 54 hours per week, depending on the nature of the work. Usual working days are also those fixed by establishments' internal regulations.

International recommendations

The definitions of basic wages (for normal working hours and days) and gross earnings conform to the guidelines contained in the international recommendations. In particular, gross earnings include regular and irregular payments in cash and in kind, and correspond to the definition used in non-current (annual) surveys. The definition of hours of work corresponds to the concept of normal hours of work.

Classifications

Industrial

The Thailand Standard Industrial Classification (TSIC) is used, which can be linked to the International Standard Industrial Classification of all economic activities (ISIC), Rev.2, 1968 at the two-digit level.

Occupational

Employment and earnings data are classified according to the Thailand Standard Classification of Occupations (TSCO) which can be linked to the International Standard Classification of Occupations (ISCO-68) at the two-digit level.

Others

Data are classified by employment size of establishments (four size groups: 1 to 4 employees, 5 to 19, 20 to 99, and 100 and over), region (six regions) and sex. Employment and wages data are also classified by level of basic wage rates (whether lower or higher than the minimum wage), and by age group and education level.

Sample size and design

Statistical unit

The sampling and reporting unit is the establishment. The ultimate unit of observation is the individual employee in each sampled establishment.

Survey universe / sample frame

This consists of the Listing of Establishments compiled on the basis of the results of the Industrial Census which takes place every year. In 1993, the sampling frame contained about 239,680 establishments, with some 4,912,000 employees. The frame is updated every year using data from the Labour Inspection and Social Security.

Sample design

The survey is based on a stratified random sampling. The sample is stratified by region (six strata: Bangkok Metropolis, five provinces around Bangkok, and Central, North, Northeast and South regions), industry and employment size (four groups). Within each stratum, establishments are selected by systematic random sampling. The sample comprises approximately 3,500 establishments, representing some 250,000 employees. Each individual employee is covered in each sampling unit. The sample is updated each year.

Field work

Data collection

This takes place between April and June, by personal visit of the staff of the provincial Labour Protection and Welfare Offices for the province area, and the staff of the Labour Studies and Planning Division for Bangkok Metropolis. Temporary enumerators are also recruited when the need arises. After data collection, all questionnaires are sent to the Labour Studies and Planning Division, for data processing.

Survey questionnaire

This consists of two major parts:

Part I provides information on the establishment (name, address, kind of business, number of employees, usual working days and working hours, and revision of wages during the preceding year);
Part II collects data for each individual employee, on:
- occupation (position or task), sex, age, length of service, education level, type of employee by type of payment (daily, monthly or per piece), and
- wages by type of payment, overtime payments and cost-of-living allowance during the reference month; and bonuses and other benefits during the preceding year.

Additional questions relate to the employer's operational expenditure during the previous two years, and to their welfare cost during the preceding year, i.e. the total amount of education cost and recreational cost for all employees together.

Substitution of sampling units

There is no substitution of sampling units in case of total non-response.

Data processing and editing

Data are processed both manually and by computer. Coding of survey responses and data editing are carried out through field work, by statistic branch officers, and through machine edit. Error records are printed out and corrected. In the case of missing or inconsistent data, respondents are contacted by telephone. Then data are keyed onto floppy disks or taped and transmitted to the Labour Information Center officers.

Types of estimates

number of employees according to a number of classifications;
average wages (wage rates for normal or usual hours of work);
average earnings;
average daily usual or normal hours of work and average working days per month;
number of employees receiving a wage rate lower than the minimum wage rate and average by industry, kind of payment, size of establishment and region.

Monthly wage rates of daily-paid employees are obtained by multiplying daily wage rates by 26 working days, so that average monthly wage rates of all categories of employees can be calculated.

Construction of indices

Index numbers are not constructed.

Weighting of sample results

Not applied. Published results reflect the sample survey results.

Adjustments

Non-response

No adjustments are made for non-response.

Other bias

No adjustments are made for any other bias.

Use of benchmark data

Not relevant.

Seasonal variations

No adjustments are made for seasonal variations.

Indicators of reliability of the estimates

Coverage of the sampling frame

The Listing of Establishments is updated each year and every effort is made to maintain it as complete as possible.

Sampling error / sampling variance

Not computed.

Non-response rate

Not available.

Non-sampling errors

Not available.

Conformity with other sources

Not available.

Available series

Published tables include average wage rates and average earnings by industry, region and size of establishment, for each category of employees (daily-paid, monthly-paid and piece-rated employees); average usual or normal hours and days of work; and average operational cost and labour cost (all the components of earnings plus welfare cost) by industry and employment size.

History of the survey

The survey was introduced in 1964 and since then, it has been conducted annually. Between 1983 and 1986, a weighting procedure was applied to the survey results, using the inverse of the sampling fraction. This procedure was discontinued as from 1987.

Documentation

Department of Labour Protection and Welfare: Year Book of Labour Statistics (annual, Bangkok). idem: Report on Wages, Earning and Hours of work Survey (annual, ibid.); published about one year after the survey reference period. Unpublished data on the number of employees by kind of payment and region, average of working days per week by industry and size of establishment, costs by industry and size of establishment, etc., can be made available upon request, on diskette and magnetic tape.

Confidentiality / Reliability criteria

The publication and release of data are subject to confidentiality rules, whereby tables may not reveal any of the particulars of individual establishments.

Other information

Data supplied to the ILO for publication

Statistics of average normal hours paid for (excluding overtime) and average monthly wage rates for normal hours of work, for employees in non-agricultural activities and specific industries are published in Tables 11 to 15 and 16 to 20 of the Yearbook of Labour Statistics.

Other sources of data

Data on paid employment in manufacturing by major group of industry are also published in Table 5B of the ILO Yearbook of Labour Statistics. These data are derived from the annual Industrial Survey undertaken by the National Statistical Office. The Industrial Survey covers all large manufacturing establishments (i.e. those with ten or more persons engaged). Its main objective is to collect basic industrial information on the number of establishments, number of persons engaged, number of employees, wages and salaries, bonuses and fringe benefits, value of raw materials, parts and components purchased, the sales value of goods, etc. The reference period for employment data refers to the last pay period of December of the year indicated, while for industrial data, it is the whole year. All persons engaged refer to persons, both paid and unpaid, who worked in an establishment at the end of the pay period nearest to December 31. It includes persons temporarily absent from work because of illness or leave with pay, but excludes persons on leave for military services, on long leave or on strike. All persons engaged are classified as follows:

unpaid workers: working proprietors, owners or business partners, members of the proprietor's household, apprentices and others who worked in the establishment for at least 20 hours a week without receiving regular pay;
operatives: persons directly engaged in the production or other related activities of the establishment and receive regular pay in terms of wages and salaries;
other employees: all employees other than operatives as defined above.

In principle, all establishments are enumerated. The survey is conducted by mailed questionnaire. Follow-up letters are sent to the delayed respondents 15 days after the original despatch of the questionnaires and, if no response is received after the second attempt, an enumerator visits the establishment to conduct an interview. The results of the Industrial Survey are published in: National Statistical Office: Report of the Industrial Survey (annual, Bangkok).