Not only did this guy not have any trouble understanding my Hoklo, he also seemed to know exactly where and how I would not understand him. He might have been skewing his vocab toward the common vocab too. In other words, seemed like he had experience talking with Hokkien speakers. At one point he said something about a big-business land lease in Cambodia and he kept switching between 租 cou (diphthong in TC) and 稅 soeh, confident that one of the two should get the job done. That was right in the one stretch in the dialog when my mind shut down and suddenly I couldn't believe it, it was like he was speaking an alien language, with a Teochew accent

The guy was "sinkheh": his parents came from Soaⁿthâu back in the day, so he was the first generation born in Siam. He makes frequent senglí runs to Cambodia and I think also Saigon. The one thing he said that really "got" me was that he thought it would be a better idea to marry a VN girl than a Thai girl (comparing non-Sino to non-Sino), "in'ūi inâng ū kámcêng", said w/o spite, "inâng" referring to VN cabó͘. (Not sure if that's the exact pronoun he used.) I mean, I vaguely suspected this from personal experience, and I'd heard plenty of jaded ângmo͘ hold forth about Thai women being cold and bô simkoaⁿ and ké cêng ké ài, ... but this guy was a local, trading and getting around from here to Saigon on what are probably the old Teochew networks...
I stay in an old neighborhood by the river, a few stone's throws outside Yaowarat (Chinatown). Much of the population is Tn̂glâng but no one seems to have a light on for Teochew. Maybe these people tried to settle in Yaowarat back in the day but got told "lír khìr sí lah".

A 60-ish restaurant owner nearby is the son of immigrants from Kwongsai who settled down south, just up from Kelantan. Speaks Mando and Canto like a Shenzhenite. He said Canto wasn't his first language. His parents came from Guilin. I asked him if bahasa Guilin was some kind of Mandarin, he said he figured it was. Then he said TO EAT in bahasa Guilin and it was something like "yaak faan" (both low level), sounded to me like Hoisan, I wondered if it was actually some kind of bahasa Ping. I asked the guy about Teochew, he told me that was mostly a Yaowarat thing. (!)
When I first got here, a few people talked to me in Cantonese. One was (I'm guessing) a Tai-Kadai speaker who worked in HK at some pt. He had a hoanná look

I'll add more from past trips to the LOS, as time and interest permit.