British citizen, domiciled in Thailand. The first time, working 'field operations' just outside Bangkok, was under a 1-year, multi-entry Non-O visa that had already been issued in Kuala Lumpur. All handled by my employer's agent in Bangkok, all very efficient.
The second time, office based, the above visa had expired and had already converted into a marriage extension that my new prospective Thai employer's HR department said could not be used for enabling another work permit. I sent my second passport to the UK with an application for a single-entry Non-O Thai visa along with the employer's supporting documents. After it was couriered back, I did an exit and re-entry via air to flip passports. After entering on the passport with the new visa, HR proceeded with getting the work permit.
I was working and getting paid for the few weeks it took to send off the passport, get the new visa, do the out/in and formalize my legal work status.
The third time, I applied for the appropriate visa in Singapore, along with the supporting documentation. After re-entering the country, the medical and other work permit related stuff was handled via the client's agents in Bangkok and Songkhla while I was offshore.
These were over a spread of about 10 years and each one was progressively more 'difficult', but since all were done under the wing of the Department of Mineral Fuels, probably still a bit easier than most?