@Jo *********
But kind of blocks future BD in Thailand. You have not read my reference to revenue generated in Australia. It's wrong to say PE is no issue. Individual cases vary. Public listed companies will be extremely adverse to trying to mislead or lie to Thai authorities. Any British company found to be doing this will not only lose work in Thailand, but almost certainly lose any chance of UK government work due to corrupt practices. Same in Australia.
Finally, it's not ok to say working with no work permit is not an issue. It's an issue when you are caught. Australia is home to about 100,000 illegal workers. You need to have a read of the Thailand Australia tax treaty. It might be similar wording to the UK version, which contains the rather vague habitual term.
PE can be established through remote working.