There is an old adage that says ‘if you can’t afford travel insurance you can’t afford to travel.’ I’m not sure who said it (probably somebody in the travel insurance industry!) but it is still valid.
Whoever you use for your travel insurance, make sure that you are adequately insured for your own particular circumstances. For instance, the insurance requirements of a retired couple on a two week vacation are likely to be very different to those of a twenty-year-old backpacker. I’ve used World Nomads before for my travel insurance* and found the process of buying online easy and convenient. Their prices aren’t always the cheapest, but often in life you get what you pay for. They are one of the few companies I’ve found that offers insurance suitable for residents of most countries (more than 150 countries are covered). The World Nomads policy also enables you to claim online, even while away from home* and is therefore well-suited to those spending an extended stay in Thailand.
Regardless of your length of visit to Thailand you should have insurance cover, particularly medical insurance and personal liability cover. If something goes wrong during your visit to Thailand you will be left with the bill to pay. Your embassy will not bail you out financially.
Your insurer should provide you with a 24-hour emergency helpline (ideally a toll-free number). For your part, it is advised to be honest about any pre-existing or current medical conditions when applying for any policy as failure to do so may prejudice any subsequent claim.