Currently the forum rules say "English is the only acceptable language"

So theoretically if one person would ask where to buy a vacuum cleaner and somebody would reply to him telling him that he should go to Homepro and ask for เครื่องดูดฝุ่น (which he could just show the people at Homepro and they would understand him 100% instead of writing it as transliteration which might not be understood), this would be against the forum rules.

Obviously nobody should make whole posts in Thai script, but in many cases it makes sense to include Thai script in a post (also for example as source).

I would suggest an update to the forum rules which says that pieces of Thai script are allowed in posts if they help the understanding.

Good point, I have made some posts over in the farming forum, and I have used Thai script a good few times over the past few years ie for names of a grass/ plants, as you said no one could understand my phonetics if I wrote it in English. 

So far I have not had a mod bend my ears, maybe in some cases, the rules can be bent a little. 

I allow Thai if it is  less than a line or 2 after checking to see what is says when translated to English.

I think most of them that get removed is because somebody reported them and the mod did it to clear the report. I will check to see what it says in English and clear the report after making a notice it was allowed by doing a post or editing the post to make a statement it was allowed unless I find it not acceptable.