@luicks
Yes, I needed a health insurance. I also had to make the insurance for a full year, and not just for the 6 months I will be staying in Thailand. And in the "Confirmation of Insurance", which is needed in english or thai language, must be written:
• min. 40,000 THB (or €1,300) outpatient
• min. 400,000 THB (or €13,000) inpatient
Important are the words outpatient and inpatient! I didn't have them in there at first, because my insurance has unlimited coverage. So it took 2 weeks, until the consulate called me and said, that they want to see those 2 words... Ridiculous!