Here's an ideal itinerary for 10 days in Thailand:

Day 1: Arrival in Bangkok

• Arrive at Suvarnabhumi Airport and check into your hotel
• Take a stroll around the city and explore the vibrant street markets
• Visit Wat Phra Kaew and the Grand Palace, two of Bangkok's most iconic landmarks

Day 2: Bangkok

• Start your day with a visit to Wat Arun, also known as the Temple of Dawn
• Take a boat ride along the Chao Phraya River and explore the canals of Bangkok
• Visit the Jim Thompson House, a beautiful traditional Thai house turned museum
• End your day with a visit to Khao San Road, a popular backpacker hub with plenty of bars and restaurants

Day 3: Ayutthaya

• Take a day trip to Ayutthaya, the ancient capital of Thailand
• Explore the ruins of the old city, including the famous Wat Mahathat temple
• Visit the Bang Pa-In Royal Palace, a stunning summer palace built by King Rama V

Day 4: Chiang Mai

• Fly to Chiang Mai, a charming city in northern Thailand
• Visit the Doi Suthep temple, located on a mountain overlooking the city
• Explore the night markets and sample some delicious local food

Day 5: Chiang Mai

• Take a cooking class and learn how to make traditional Thai dishes
• Visit the Elephant Nature Park and spend the day interacting with rescued elephants
• Relax with a traditional Thai massage

Day 6: Chiang Rai

• Take a day trip to Chiang Rai, a city known for its stunning temples and natural beauty
• Visit the White Temple, a unique and beautiful temple designed by a local artist
• Explore the Golden Triangle, where Thailand, Laos, and Myanmar meet

Day 7: Krabi

• Fly to Krabi, a beautiful coastal town in southern Thailand
• Relax on the beach and soak up the sun
• Take a boat tour of the nearby islands and explore the stunning limestone cliffs and crystal-clear waters

Day 8: Krabi

• Visit the Tiger Cave Temple, a Buddhist temple located in a cave high up in the mountains
• Go rock climbing or kayaking in Railay Beach
• Enjoy a seafood dinner at one of the many restaurants along the beach

Day 9: Phuket

• Take a ferry to Phuket, Thailand's largest island
• Visit the Big Buddha, a giant statue overlooking the island
• Explore the old town and its colorful Sino-Portuguese architecture

Day 10: Phuket

• Spend your last day in Thailand relaxing on the beach and soaking up the sun
• Take a sunset cruise and enjoy the stunning views of the Andaman Sea
• End your trip with a delicious Thai dinner and some drinks at one of the island's many bars and clubs.

I hope this itinerary helps you plan your trip to Thailand!