While it seems many Thais are too lazy to actually pronounce an "r" in quite a few words; remarkably they can get it right when there is more than one "r" sound in a multi-syllable word or when its used in a consonant cluster

. Also when a word has an "L" they never substitute an "R" for it instead. It seems to be a one-way sound substitution only like; an
ร can sometimes be said as an
ล, but an
ล can never be said as an
ร 
. Strange rule really.
In colloquially spoken Thai the "L" for "R" dealy carries abso-tively posi-lutely no loss in comprehension when foreigners are speaking to Thais. In fact, about the only people I ever hear who're "rolling their r's" are; "pretentious Thais" who wanna appear smarter than they are, or foreigners who were taught to over pronounce it that way in Thai language schools. Heck even Thai newscasters (admittedly not the highest caliber of newsreaders in the known universe

) get it wrong when reading the Thai news, so go figure.
A lotta times when I ask a Thai to spell a word which I've heard them pronounce with an "L" but know has an "R", I'll ask 'em in Thai something like; Is that word spelled with
รอ-
ลิง or
ลอ-
เรือ? Granted, purposely mixing up the picto-words associated with each consonant can be construed as condescending

, but it's also a form of word play. I've only had Thais laugh and joke with me about it, so it must be okay with them too

.
I'd hafta disagree about
ร being anything other than an "R" in English, no matter what engrish karaoke system you're using to represent the Thai sounds. Now I'm not talking about final consonant ending sounds, or
รร, or
ร์, just the normal "R" sound
ร makes.

..
Personally I wouldn't give it a second thought. FWIW; most Thais think foreigners speak Thai with a
ลิ้นแข็ง (hard tongue) or a
สำเนียงแปลก ๆ (very unusual accent) anyway. .

.
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