ฤ (rue,ri) is special vowel in Thailand dictionary. This letter comes from the Sanskrit language.
The original pronunciation is ''ri''
How to pronounce When it was amalgamated with the letters in the Thai language.
1. if ฤ no initial consonant will read aloud all ''rue , ri and rer''
example : ฤดู (rue-du) , ฤทธิ์ (rid) and ฤกษ์ (rerg) is a single word that is ''rer''