What historical period are you interested in for Thailand/Siam? This book is more about the Bangkok era (Chakri dynasty) and a bit about Ayutthaya. I've read an earlier edition and it has quite good detail and gives some emphasis to socio-economic and cultural issues although I don't necessarily agree with the author's slant on the historical players' motivations. https://www.amazon.com/History-Thailand-Chris-Baker/dp/1107420210/ref=pd_sbs_14_1/136-1976880-2390160?_encoding=UTF8&pd_rd_i=1107420210&pd_rd_r=T1ZB5HCW406BD6W9FT4B&pd_rd_w=RNEff&pd_rd_wg=i71bB&psc=1&refRID=T1ZB5HCW406BD6W9FT4B