Yes, there is no need to worry about street crime or aggressive behaviour, Thais are a gentle people with a friendly nature. The vast majority of European cities are far worse off in terms of security than Koh Samui, or the rest of Thailand for that matter.

Consumption of money on vacation is a completely individual matter and despite the fact that most goods and services are cheaper in Thailand than in the Czech Republic, for example, alcohol is more expensive. For a draft big beer it is not a problem to pay 130 Baht (90 CZK) in a restaurant and 60 Baht (42 CZK) in a convenience store. If one does not restrict oneself too much, or does not "splurge", it is possible to count on about 15000 Baht per person for a 10-day holiday. This is about 10500 CZK. In this budget one can count on renting a scooter, taking 2 trips, entrance fees to some attractions and good food in cheaper but good quality restaurants, including some beer or other drinks to improve the mood. In Thailand you must use the local currency Baht, so Euro or Dollar is recommended, which you can exchange at any bank, which is practically on every corner. Nowadays you can also buy Baht directly in the country, but at less favourable rates.

No vaccinations are required for Thailand, however it is recommended to have tetanus (at least know when I was last vaccinated) and hepatitis. This applies generally to travel anywhere. It is possible to get vaccinated for typhoid and other tropical diseases, in my opinion such vaccinations are rather detrimental, they are a burden to your system before the trip and also to your wallet. There is no need to worry about malaria on Koh Samui,the ever present mosquito borne dengue fever is still present but the risk of getting sick is quite low.

Koh Samui has a number of high quality hospitals with modern facilities and professional staff. The local facilities try to make the stay in the hospital, if it happens, pleasant enough for the customer to enjoy their holiday as much as possible. The quality of care, however, goes hand in hand with the price, so clearly we recommend that you have travel insuranceotherwise the hospital bills will climb into the astronomical, no problem, hundreds of thousands to millions of dollars.

I don't recommend drinking tap water, although the water from the line is chemically treated and shouldn't be a problem, it's better to buy bottled water, or use local water machines where you can very cheaply fill your own containers (1l for about 1 Baht - in a shop 1l will cost you 10 times or more). You can use tap water to shower, brush your teeth and even pour over your coffee after boiling. On the other hand, you don't have to worry about the food from the stalls at all,on the contrary, I recommend to try the variety of Thai cuisine and instead of an expensive dinner in a restaurant choose to visit the local market with stalls and eat royally for a few pennies. Be careful only with unprepared food such as salads, raw (dried) fish and seafood (typically squid). Sushi, for example, or fried worms are not to be feared.