I would advise him to Wat Phra Kaew, because Wat Phra Kaew is the importance place of Thailand and also beautiful place.
And I would advise he eat Tom yum Kung, because Tom yum Kung is thai food and has delicious
And another place that I would recommend he go to Ayutthaya because Ayutthaya is a important history point of Thailand, and is also a place with many beautiful temples.