So I have been doing further research.
When I look at the list of documents required for a Non-B visa for Business in Phnom Penh, KL, Singapore or Penang, it doesn't mention anything about the need for a proof of residence for that country where I am applying. (For Singapore it says 'If applicable, a copy of the applicant’s long-term pass' and for KL it says 'A copy of Malaysian pass. (If Applicable)' so it looks like it's ok not to have that in both cases.)
However, to apply for a Non-B in Delhi or Mumbai it says that 'Proof of residence in India (if not Indian national)' is required. I do not know what constitues a 'proof of residence' but I guess I would need more than a hotel booking which is all I could provide.
To apply for a Non-B in Australia it states that I must provide 'Australian Electronic Visa (VEVO) for a proof of residence in Australia (only for non-Australian passport holders)' however you only get a VEVO for a work or study visa, not for a tourist visa. I will only have a tourist visa.
Therefore I think that I cannot apply in Australia or India, and I will need to apply in Singapore, Malaysia or Cambodia.
Please can anyone tell me: Once the Non-B visa (single entry, 90 days) is approved does the clock start ticking on the 90 days straight away? Or do you enter Thailand and then the clock starts ticking? If it is the second case, how long do I have from the visa being granted to enter Thailand? (i.e. how long is the visa valid?)
Many thanks if anyone can tell me.
(P.S. I know it is possible to get a Tourist Visa converted to a Non-B but the company I'm working with don't want to do it this way.)