ESEARCH ARTICLE R ScienceAsia 47 (2021): 618–628 doi: 10.2306/scienceasia1513-1874.2021.067 Ambient thermal comfort analysis for four major cities in Thailand, Cambodia, and Laos: Variability, trend, factor attribution, and large-scale climatic influence a,b a,b, a,b c Kimhong Chea , Kasemsan Manomaiphiboon ∗, Nishit Aman , Sirichai Thepa , Agapol Junpena,b, Bikash Devkotaa,b a The Joint Graduate School of Energy and Environment, King Mongkut’s University of Technology Thonburi, Bangkok 10140 Thailand b Center of Excellence on Energy Technology and Environment, Ministry of Higher Education, Science, Research and Innovation, Bangkok 10400 Thailand c School of Energy, Environment and Materials, King Mongkut’s University of Technology Thonburi, Bangkok 10140 Thailand ∗Corresponding author, e-mail:
[email protected] Received 26 Nov 2020 Accepted 14 Apr 2021 ABSTRACT: Characterizion of ambient thermal comfort using a standard heat index (HI) was performed for Bangkok, Chiang Mai, Phnom Penh, and Vientiane, with data covering 37 and 17 years for the first two and last two cities, respectively. HI was lower during the night and the early morning but high in the afternoon in both the dry and the wet seasons. Its diurnality showed a tendency to be more influenced by temperature than by relative humidity. The daily maximum heat index (DMHI) was the highest in April–May due to both warm and humid conditions, but was the lowest in December–January due to cool dry air. Among the five considered risk DMHI levels, “extreme caution” occurred the most often for the majority of the months, and “danger” occurrence tended to increase in April–June.