Hello! That sounds like an exciting trip to Thailand. Here are some travel tips for visiting Bangkok, Chiang Mai, and Nakhon Si Thammarat.

Best Time to Visit:
The best time to visit Thailand is from November to February. This is the country's dry and cool season. However, if you prefer fewer crowds, consider going during the rainy season which runs from July to October.

Route and Accessibility:
Bangkok, being the capital city, is easily accessible from various parts of the world through air transport. To reach Chiang Mai from Bangkok, you can take a flight, a bus, or, if you like scenic rides, a train. Nakhon Si Thammarat can be reached via a short domestic flight from Bangkok or a bus ride from several Thai cities.

Accommodation and Booking:
Thailand has abundant accommodation options from luxury hotels, budget hotels, guest houses, to hostels. Websites such as Booking.com, Agoda, and Airbnb can in finding places that fit your budget. It's advisable to book accommodation in advance, especially during the peak season.

Clothing and Essentials:
Pack lightweight and breathable clothes due to Thailand's tropical climate. Sunscreen, a hat, and sunglasses are essential. When visiting temples, cover your shoulders and legs in respect of the local custom.

Health and Safety:
Avoid drinking tap water in Thailand - always choose bottled water. Be wary of street food hygiene, especially in rural areas. Also, don't forget your travel insurance. It's also advisable to take precautions against mosquitoes due to the risk of dengue fever.

Local Etiquette and Respect:
When visiting temples, always dress modestly and avoid pointing your feet towards Buddha statues. It's respectful to wai (placing both hands together with a slight bow) when greeting. Always ask for permission before taking photos of locals.