I've got one 3 times at BKK with no problems. Make sure you have a photo as sometimes the photo machine is broken and they send you back outside to get one. Usually they just do everything for a 200 baht compulsory fee. It's up to you to weigh up the risk of it not being available and losing your permission to stay vs time at immigration.
Technically they are incorrect because it doesn't mention during the validity period. It gives a blanket statement that there is no need for a re-entry permit when one may be required during the final stay previously mentioned in the article. Anyway I just think it needs clarification. But up to you.
Their O-A advice is wrong. Bank funds are in home country bank. The income letter doesn't require an affidavit. Also METV need a reentry permit during the final extension. I didn't read the whole thing. There may be more errors.
At Hua Hin they are not too fussy about tm28 reporting. I did one when I returned from Australia to my condo room and they said don't worry about it next time unless your address in Hua Hin changes.