So you are specifically reminding all your customers that they MUST contact you if any declared circumstances change during the 72 hours prior to arrival. And you don't charge for amendments. And you acknowledge it is impossible to predict illness. Additionally, you certify that your servers and other systems will delete all personal data, including medical data, after submission of the TDAC data, including emails sent by by the Thai authorities in relation to the TDAC submission. GDPR and PIPL both contain specific requirements concerning health records, which includes vaccination records. Individuals submitting data to a government organisation creates one set of restrictions..it's a different matter concerning 3rd party unofficial organisations.
Companies offering this as a paid service are going to find themselves in a lot of legal bother. Depending on travel history in the weeks before travel, travellers may be asked to complete a form on symptoms. Not only is this completely worthless if the form is filled in a month or more before travel, I doubt any of these firms are even legally allowed to process and secure someone's medical history. Currently if you have traveled to a country on the Yellow Fever list, you will be asked to complete a questionnaire on symptoms experienced, such as a sore throat, runny nose, a cough. The Thai government can change the country criteria at any time they like. Currently, this includes Brazil, Argentina, Colombia, Trinidad, Venezuela, hardly obscure countries. If the company offering the service fills this information in themselves, they are committing fraud. So.is the traveller, because the traveller is supposed to be telling this to the Thai government not a third party. In addition, many people will have unplanned travel, such as for work, which might not be captured if they fill out a form weeks in advance. Those charging for the service are exploiting fear and ignorance, and making hay. And just like those companies trying to exploit immigration loopholes, this will eventually ruin it for others. The form is very easy, takes less than 2 minutes.
Home Office might worry thst a low paying teaching job in Thailand isn't enough reason for her to return home. Her parent's might well be dead given her age. The bar girls aren't looking a holiday fling. Stick in an application now. It's going to cost you £120 or so to find out, unless she wants to use an agent. Agents can ensure that she doesn't make a mistake in the application, and can advise on the invitation letter. You need 6 month bank receipts, proof of accommodation, such as mortgage statement, deeds, lease agreement. I also provided salary slip.
If she is not paying for the entire trip herself, you should write a letter of invitation, explaining the nature of your relationship. She has no dependants and no concrete ties to Thailand besides a nondescript job. She can't afford the trip herself. I only know what works for me, which involves marriage, registering a business, making a sure a bank account has money in it. My wife had a 5 year black listing in Malaysia.
I haven't had a problem, but others have. Note, no matter how long she says she will stay in the UK, the visa is always for 6 months. Do you know what travel history she has had before. Does she own property. Does she have 100,000 in the bank. Does she have children or elderly parents. Who is paying her expenses to and in the UK?
While that might (or might not) address medical concerns, it doesn't change medical history one iota. High blood pressure can lead to irreversible damage, and so it's often treated as a life long chronic illness, in that you will always be prone to high blood pressure requiring medication or an unusual change in diet.