Does my friend need to be vaccinated and buy insurance for travel to Thailand from Cambodia?

As of June 1, according to The Phuket News:

“Upon arriving in Thailand, all travellers must undergo entry screening, including body temperature check, and present the required documents to the Immigration/Health Control officer to carry out the checks.

The vaccinated travellers will then be allowed entry and are free to go anywhere in the kingdom. *For arrivals by land using a border pass, they will be allowed a stay of no longer than 3 days within the specified areas only.

Likewise, unvaccinated/not fully vaccinated travellers who have uploaded proof of a negative result from an RT-PCR test or professional ATK within 72 hours of travel via the Thailand Pass system will be allowed entry and are free to go anywhere in the kingdom.

Unvaccinated/not fully vaccinated travellers without a negative test result within 72 hours of travel are required to follow the public health instructions and guidelines as deemed appropriate by the Health Control officer at the point of arrival.”

Insurance is required.

If she's not vaccinated then she needs to submit a clinical test certificate within 72 hours of travel as part of the Thailand Pass application. You can't submit the application until you have the test.

Insurance is required for everyone that's not Thai.