Been wondering for a while what Bhum Jai as in political party stood for, couldnt find anything in my dictionarys anywhere near.

Now I find it is supposed to be the proud thai or pride in Thailand party.

With proud as in ภูนใจ.

Also I often see W transliterated a v as in Vibhavadi Hospital, Navawakorn etc.

Cant work out why they do this, anyone know if there is an explanation?

Because people don't know about or take no notice of the Royal Institute's system of transcription.

http://en.wikipedia....f_Transcription

It's quasi-etymological spelling. The ภูมิ part of ภูมิใจ is a Sanskrit word, written and pronounced bhūmi (or, less technically, bhumi). As you can see, Thai spelling is far more conservative than its pronunciation. I say "quasi" because of course they've opted to ignore the i in ภูมิ, as it's not pronounced in Thai, despite using the Sanskrit spelling of the letter ภ.

It's the same basic reason why ว is often written with v, why สุวรรณภูมิ is pronounced Soo-wunna-poom but spelled Suvarnabhumi, and so forth. It's a mess. I think these Sanskrit spellings carry an air of erudition and tradition for educated Thais, even though they don't usually fully understand why things are (or aren't) spelled how they are, as few people get a solid grounding in Pali and Sanskrit anymore (just like few English speakers learn the Greek and Latin roots of English words anymore). I think most Thais are as confused as you are about the matter.

The Royal Institute decided decades ago to make the standard system for writing Thai phonetic, but before that, Sanskritized spellings were the closest thing to a formal standard. In 1913 King Rama VI published his system for romanizing Thai, based on the standard system for romanizing Sanskrit (IAST), but including some changes to account for phonetic Thai pronunciation. (See Wikipedia for a full set of Thai/IAST equivalents.)

That system remained the norm for a long time. This was also the era when Thais began to adopt surnames, and Rama VI himself coined some 6000 surnames from Pali and Sanskrit words, and bestowed them upon royalty and bureaucracy. When he bestowed the last names, he also bestowed a prescribed English spelling. (There used to be a site on the Army Medical Department website, of all places, that listed them all, but it appears they killed it when the recently upgraded their site. Here's one section, the letter พ, courtesy of Google cache.)

So even when the official system for writing Thai became phonetic decades later, most personal names and other proper remained unchanged.

This has left us today with a jumble of spellings, a mixture of multiple phonetic schemes and Sanskrit spellings, often within the same word!