I should say I have trained with Fukakusa shihan for several years, and was about when Renbukan dojo was set up, although I'm currently back in the UK.
I beg to differ a little from Taka's previous post in that actually sensei teaches most nights, albeit not always at the Renbukan dojo (the HQ dojo at Phrakanong BTS station -- which, incidentally, is really easy to get to).
Fukakusa shihan also teaches the Thai military in their own facilities (several of his yudansha are ranked military), as well as practical self-defence to (all) the Thai Airways cabin staff. So his background is immensely practical. However he has always made the distinction between self defence and aikido clear, and in the aikido classes what you'll get is classical aikido.
More so than any other teacher I have trained under, Fukakusa shihan moderates his technique according to the people he is teaching, and the partner he's throwing. This is, I believe, an indication of admirable modesty (which is the mark of somebody with nothing to prove, something that some other teachers are sadly lacking in aikido) because if you've ever seen him really, uh, cut it up, you'll know that he has immensely powerful technique. (He's also very fast when he wants to be!) He is, however, a very polite man and a wonderful teacher -- especially to polite beginners. Of course, you should bear Taka's report in mind because that too is based on experience, but when I was resident in Bangkok, I often attended classes with Fukakusa sensei six nights a week.
It's also worth noting that sensei has been teaching in Bangkok since he was sent there (by Tamura shihan, who was still in Japan at the time) forty years ago, so some of the other senior instructors whom he has raised are pretty impressive in their own right too. Basically, Bangkok is a great place to train in aikikai aikido. Fukakusa shihan is also a popular and admired teacher in the region -- he set up the AAF and, incidentally, this is a good time to remind people that time's running out for application to the AAF congress in November -- for more information about this (and the dojo locations/timetables) see http://www.thaiaikikai.com
I have to say I enjoy the "weird mix of language", if that's what it is! The primary language of instruction is Thai of course, but as sensei and some of the shidoin are Japanese, of course Japanese is spoken if there are Japanese students on the mat (as there often are). As a courtesy to the many foreigners who join in at the Renbukan dojo, English is common too. Incidentally, at Din Daeng dojo, it's generally all in Thai, whereas at Dance Centre dojo it's all in English.
Incidentally, Taka, I think you're probably completely, er, right
when you say it seemed a bit unstructured compared to what you're used to... but I think that's what you'll find at any aikikai dojo
Also, as I said above, there's quite a range of teaching styles amongst the seniors there.
Of course, bear in mind that I am a student of Fukakusa shihan, so my opinion is bound to be biased... YMMV