Cold, never a term you associate with Thailand or this region of the world and certainly not a term associated with Bangkok. Bangkok is constantly listed as the major metropolitan are with the hottest climate, this article cites the World Meteorological Organization calling Bangkok the hottest city in the world with an average temperature of 28c.
Bangkok and Thailand are built for heat, not cold. Many traditional house have high ceilings, allowing the heat to rise. Houses and offices do not have heaters, only air-conditioning. Of course this was a massive change after living in San Francisco as most homes in San Francisco do not have air-conditioning, but all have heaters. And just as a heat-wave causes major problems in San Francisco, a cold spell poses big problems for Bangkok and Thailand.
On Thursday, 23 January the reported low temperature in Bangkok was 15.6c, that is a 30-year low as detailed in this AP article. Yes, I know many people in Europe and parts of the US will scoff and say 15.6c (60f) isn’t cold, but more than 63 people have died in Thailand from this cold spell (many of the deaths have been in the north and northeast where the temperature has been as low as 8c).
After living in Thailand for 3 years, my body has acclimated to the heat, suddenly 16c feels cold. Thais are not used to this kind of cold weather, many Thais can sit in 34c heat, eating a bowl of hot soup without sweating, they are not used to 16c.
People are wearing layers of clothes, big coats and even gloves. Even animals are cold- many dogs are laying in the sun and owners have put shirts on their dogs to keep them warm.
It is cool here and the 15.6c temperature is shocking, as it should be, that is over 40% less than the average daily temperature.
Farang ( ฝรั่ง) In Bangkok 
Your blog is interesting. I live in SF, too, and wonder what you do in Thailand? And as you probably know, it’s been a warm, dry, dry winter here. On your next trip back, bring some tropical rain with you. We need it badly.
I love the cool weather, normally I have to turn on the air con in my room in Huai Kwang every night, but this was the first “winter” where I slept without aircon (and fan) for more than two months, loving it! I remember last year we only had about 2 or 3 nights where the temperature dropped below 20 degrees Celsius.