I also have a thing for old dictionaries. Take my digital critical edition of the first Thai-English dictionary as proof of that. It's based on a mid-19th Century manuscript of unknown provenance in the British Museum. I gradually typed out the 500-page document over the course of 2006. It was roughly equal parts fascinating and tedious. I got pretty good at reading the chicken-scratch English. The Thai is much more easy to read, ironically, despite a few orthographic quirks of the era.
I typed it up from a digital scan made of a microfilm copy of the manuscript. Since old dictionaries are so hard to find in the flesh--er, paper--a decent scan will do. And thanks to such scans I've been able to examine many early Thai dictionaries. No doubt, without this technology I never would've gotten to read through them closely even if I did find them in some library.
Recently I've been enjoying E. B. Michell's 1892 work A Siamese-English Dictionary, For the use of students in both languages. The book is in the public domain, and downloadable from Google Books within the United States, or viewable on SEAlang. I don't know much about Michell other than what the title page says: "M.A., Barrister-at-Law, late Legal Adviser to His Siamese Majesty's Government." The Majesty in question here is King Chulalongkorn, or Rama V, who reigned from 1868 to 1910. Google tells me Michell's full name is Edward Blair Michell, and that's the extent of my knowledge of him.
I posted last month about finding 'copy' in this dictionary, spelled กอปี้, whereas today it's usually spelled ก๊อปปี้. As it turns out, there are a number more loanwords that Michell says come from English. And interestingly, all of them are still used:
ไปรเวต = private; I've only seen this used nowadays to refer to casual attire. I first encountered it when my wife and I had pictures taken before our wedding. We had pictures taken in a few different outfits, including ชุดไปรเวต. This usage must be uniquely Thai, because 'private outfit' doesn't sound like anything I'd normally have my picture taken in.
แปลน = plan; I still hear this used as an alternative to แผน. I don't know the etymology of แผน, but it seems to be preferred as the native (or more native sounding?) alternative to แปลน.
แหม่ม [แหฺม่ม] = Ma'am; this has gone from referring to a woman Westerner to being a very popular girl's nickname.
ออฟฟิศ = office; it's even still spelled this way, with the final ศ. You can usually spot a loanword as being of 19th Century origin by the presence of these less common letters usually reserved for loans from Pali and Sanskrit. Two other examples are โปลิศ 'police' and อังกฤษ 'English'.
บ๋อย = boy; this specifically refers to a servant boy or a waiter. I still hear this around.
บิล = bill; everybody knows this one, don't they? Pronounced 'bin' in the typical Thai way, and nowadays usually paired with 'check' เช็ค as เช็คบิล used to ask for the check at a restaurant. In this context, 'check' and 'bill' are actually two words for the same thing. I would hypothesize that if 'bill' was already in the language, and so was 'check' in the verb sense 'to check, to examine', then the influence of English 'check please' in the restaurant setting influenced the birth of the quirky Thai-ism 'check bill', which in the Thai context it means to literally check the bill.
แบงก์ = bank, meaning the financial institution; more commonly spelled แบงค์ nowadays.
ปิ่น = pin; used for one's hair. Immortalized in Thai in phrases like ปิ่นเกล้า pin klao, a pin for holding the hair in place when pulled up on the crown like a bun.
ฟุด = foot (the unit of measure); nowadays spelled ฟุต, reflecting the final t of the English spelling.
มรสุม [มอ-ระ-สุม] = monsoon; I don't think this is actually from English as Michell claims. Etymonline traces its route into English as Arabic > Portuguese > Dutch > English:
"trade wind of the Indian Ocean," 1584, from Du. monssoen, from Port. monçao, from Ar. mawsim "appropriate season" (for a voyage, pilgrimage, etc.), from wasama "he marked." When it blows from the southwest (April through October) it brings heavy rain, hence "the rainy season" (1747).I'd say it's quite plausible that it came into Thai from Arabic, perhaps through Persian (which has many Arabic loans), since Thai has other words of purported Persian origin, like องุ่น 'grape', กุหลาบ 'rose', and กะหล่ำ 'cabbage'. Also notice that 'morasum' is slightly closer to 'mawsim' than to 'moncao' or 'monssoen' (but not conclusively so). If it's a newer loan, it may have come through Portuguese, which gave Thai at least one other early loanword, สบู่ 'soap'.