What proof of residency in Malaysia is needed when applying for a Thai non-B visa?

A British citizen currently in Thailand is seeking guidance on applying for a Thai non-B visa while in Malaysia. The traveler is concerned about the proof of residency required for the online application and whether evidence such as a visa stamp from Malaysia is sufficient. There is also a question regarding acceptable proof of finances, particularly if the bank statement address must be in Malaysia or can remain in the UK. One response advises that visa waiver entry does not count as proof of residency and mentions that Malaysian consulates typically serve only Malaysian residents.