Hello! It sounds like you're planning an exciting trip to Thailand. Here are some tips to make your trip smoother and more enjoyable.

Best Time to Visit:
The best time to visit Phuket, Pattaya and Bangkok is between November and April when it's relatively cooler and dry. This is also when most of the country's major festivals occur, like Songkran (Thai New Year) and Loi Krathong (Lantern festival). However, if you plan to do a lot of outdoor activities or beach visits, do check the weather forecasts.

Route and Accessibility:
All three cities are seamlessly connected by road and air. Bangkok has two international airports- Suvarnabhumi and Don Mueang, from where you can take domestic flights to Phuket or Pattaya. For road transport, you can rent cars, use taxis, or catch buses. In the cities, Tuk-Tuks are a popular mode of transport.

Accommodation and Booking:
Accommodations range from budget and mid-price hotels, to luxury resorts. It's generally easier to find good deals online, and it's advisable to book in advance, especially during the peak season. Make sure to check customer reviews and ratings before booking.

Clothing and Essentials:
Lightweight, breathable clothing is recommended due to the hot and humid climate. Don't forget your swimwear for beach visits. A sun hat, sunglasses, and strong sunscreen are essential. Carry bug repellent, and if you plan to visit temples, pack clothes that cover your shoulders and knees.

Health and Safety:
Tap water in Thailand is not potable so always drink bottled water. Health services are good especially in Bangkok with a wide range of private hospitals. As safety precaution, avoid less crowded regions at night and keep your belongings secure.

Local Etiquette and Respect:
Thais appreciate it when visitors respect their customs. This includes removing shoes when entering homes or certain temples, not touching anyone's head (considered sacred), refraining from pointing at things with your feet, and being respectful towards images of Buddha and the monarchy.