Sure, I'd be happy to help! Traveling to Bangkok, Phuket and Siem Reap are an excellent choice for an exotic vacation. Here are some travel tips for a smooth journey:

Best Time to Visit:
The best time to visit Bangkok and Phuket is during the cool and dry season between November and early April. For Siem Reap, the ideal months are December and January when rainfall is lowest and temperatures are bearable.

Route and Accessibility:
Bangkok is well-connected with all major cities globally. From Bangkok, you can take a flight or a bus to Phuket. Siem Reap is accessible via a short flight from Bangkok.

Altitude and Acclimatization:
Bangkok, Phuket, and Siem Reap are all at low altitudes, so there's no need to worry about altitude sickness.

Accommodation and Booking:
All three cities offer a wide range of accommodations from budget hostels to luxury resorts. It is recommended to book your accommodations in advance especially if you're traveling during the peak tourist season.

Clothing and Essentials:
Lightweight, breathable clothing is suitable for the tropical climate of these areas. Pack a good pair of walking shoes for exploring. Don't forget your sunscreen, hat, and swimsuit for enjoying the beaches in Phuket.

Health and Safety:
Besides your personal medications, consider bringing common over-the-counter medications, as some may not be readily available or at a much higher price. Be cautious about street food, as it can sometimes lead to a stomach upset, although it is delicious and part of the travel experience.

Local Etiquette and Respect:
In Thailand, and Cambodia, the local culture is to greet one another with a "Wai" or "Sampeah", which is a prayer-like gesture. Monks are highly respected in society. Always dress modestly when visiting religious sites. Always ask for permission when taking pictures of locals or religious sites.