I think you're getting distracted by side issues and missing the main point. Firstly, saying "Brits can't" because most Welsh people don't speak Welsh is a rather odd argument. You appear to be using "Brit" when you actually mean "English". Britain contains several nations and languages, and Welsh is one of them. As for personal anecdotes, they're not particularly useful. Where I used to live, nearly half the population spoke Welsh. In Gwynedd, around Caernarfon, Welsh speakers account for roughly 65% of the population. In one workplace I was the only native English speaker, and some colleagues spoke little or no English at all. Welsh language use is much lower in much of South Wales, but that's a different discussion entirely. More importantly, none of this has much to do with the subject under discussion, which is foreign speakers, pronunciation, and transcription systems. Many non-Welsh speakers can correctly pronounce and spell “Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch”, but that doesn't mean Welsh spelling follows English phonetic rules. Welsh, uses the Latin alphabet but assigns different values to letters and combinations of letters. Sounds such as the unvoiced "ll" and the guttural "ch" simply don't exist in English. The earliest written Welsh dates back to around the 6th century and was written using the Latin alphabet, yet nobody would claim Welsh spelling should be interpreted through English pronunciation rules. The same principle applies to Thai. There can never be a perfect system for transcribing Thai into English because Thai contains sounds that simply don't exist in English. Various transcription systems attempt to bridge that gap, each with different priorities. The RTGS system used on road signs prioritises simplicity, while academic and language-learning systems often prioritise accuracy and pronunciation. This brings us back to "farang" and "farlang". The difference isn't really about Thai speakers substituting L for R in casual speech. That's a separate issue. In informal Thai, many speakers replace the rolled or trilled ร sound with ล or sometimes omit it entirely. That's normal conversational Thai and varies by region and dialect. The problem with "farlang" lies elsewhere. Your transcription changes the vowel sound in the first syllable. The Thai word is ฝรั่ง. The first syllable contains a short vowel sound, something closer to "fuh" than "far". It’s like the “schwa” sound...almost….There is no recognised transcription system in which "far" accurately represents that syllable. So while "farang", "falang" and similar spellings are commonly encountered, "farlang" isn't simply reflecting an L-for-R substitution. It is also introducing a vowel sound that isn't present in the original Thai word. You asked why it matters if people understand what you mean. The answer is that we're discussing why foreigners mispronounce Thai words and how transcription influences that process. If people invent spellings based on what they think they hear rather than using an established transcription system, they often end up reinforcing incorrect pronunciations. It's the same issue that arises with "Jomtien". Many foreigners naturally turn the final N into an M because of a normal speech process called anticipatory assimilation. That's understandable. But writing down an inaccurate transcription and then treating it as if it reflects the original Thai pronunciation is a different matter entirely. Many people don't realise there isn't just one system for converting Thai into the Latin alphabet. Some systems focus on reproducing pronunciation, while others focus on preserving the original spelling. RTGS, ISO 11940, ALA-LC and various language-learning systems all approach the problem differently. As a result, the same Thai word can legitimately appear in several forms depending on the system being used. What they all have in common, however, is that they are structured systems. They are attempts to represent Thai sounds and spelling consistently. Simply making up spellings based on personal interpretation is neither transcription nor transliteration; it's guesswork. That's why I pointed out "farlang". Not because people don't understand what you mean, but because it illustrates exactly how inaccurate transcriptions can distort both pronunciation and understanding of the original Thai word.
