*2.1. Research Design*

A cross-sectional survey using structured questionnaires was completed by face-to face interviews. Adult migrant workers (18 to 60 years old) who were willing to participate in the study by voluntarily giving written informed consent were recruited.

#### Population and Study Population

Sample size was calculated by using the Taro Yamane formulae, with reference to the total population of 81,299 Myanmar migrant workers in Chiang Mai province [10]. A sample size of 398 was calculated, and it was increased by 5% to compensate for incomplete data.

#### *2.2. Research Instruments*

Questionnaires were validated in the languages of targeted population, both in Thai and Myanmar versions. Following the WHO process of instrument translation and adap-

tation process, researchers investigated the readability and comprehension of the questionnaires by a pilot study including thirty migrant workers who voluntarily consented to participate. Pilot study participants were similar to the potential participants planned to be recruited in the future cross-sectional surveys in that they were (1) an immigrant person from Myanmar to Chiang Mai, Thailand, for labor; (2) ethnically either Myanmar or Shan; (3) either male or female gender; and (4) willing to participate in the research. The pilot study was conducted in March 2016 in Chiang Mai, Thailand [11]. The questionnaires were revised upon reviewing the results of pilot study to develop a final version. Validated questionnaires consisted of 3 parts to explore both modifiable and non-modifiable risk factors for hypertension: (1) socio-demographic characteristics, (2) health behaviors, and (3) measurements. Socio-demographic characteristics of the study participants included age, gender, history of chronic diseases such as diabetes, educational attainment (no formal education, primary school completed, and secondary school and above), marital status (single or married), types of job, and years of stay in Thailand. Regarding health behaviors, smoking and drinking alcohol, sleeping hours per day, and exercise habits were included. "Current smokers" were defined as those who smoked any tobacco products either on some days or every day. Former smokers or those who never smoked cigarettes were categorized as "current non-smokers". Those who consumed any type of alcoholic drinks (spirit, beer, wine) regularly or irregularly during the previous year were categorized as "current alcohol drinkers". Exercise activity was assessed: type of exercise such as walking, running, playing football, or playing badminton; duration of each exercise session; and number of exercise sessions per week were recorded. Measurements of height (m), body weight (kg), waist circumference (cm), hip circumference (cm), and blood pressure (mmHg) were completed.

### *2.3. Data Collection*

The study participants were recruited with their written informed consent during the whole month of December 2017. The research team recruited the participants while they were waiting for the registration process at the provincial employment office, Chiang Mai. Data collection was completed using a stratified sampling technique and face-to-face interviews by the trained research assistants who were able to speak the languages of the study participants (Thai, Myanmar, and Shan languages).

A portable stadiometer was used to measure the standing height without shoes (m) and a weighing scale to measure the body weight without any jacket (kg). Body mass index (BMI) was determined by calculating weight (kg)/height (m<sup>2</sup> ).

Using a standard measuring tape, measured to the nearest 0.1 cm, the midway between the lowest palpable rib and the anterior superior iliac crest was measured as waist circumference (cm), and the widest part of the buttock as hip circumference (cm). Additionally, then, waist/hip ratio was calculated to determine whether central obesity was present or not.

Digital sphygmomanometer was used to measure blood pressure. Following NICE guideline, measurement was repeated after taking rest for 5 min for those whose initial blood pressure measurement was over 140/90 mmHg to avoid white-coat hypertension [12].
