Cambodian Prime Minister Hun Sen arrived at Government House for talks with Prime Minister Prayut Chan-o-cha on Friday morning, beginning a two-day visit - his first in 12 years.
The two leaders inspected a guard of honour before entering the building to begin discussions.
This afternoon Hun Sen and his delegation are to meet Thai business representatives at the Dusit Thani Hotel in Bangkok.
On Saturday a joint Thai-Cambodian cabinet retreat is planned at Government House.
Both prime ministers are to witness the signing of a memorandum of understanding on labour cooperation, a Thai-Cambodian agreement on employment, a memorandum of understanding on a new border crossing between Ban Nong Ian village of Thailand's Sa Kaeo province and Stung Bot area of Cambodia's Banteay Meanchey province, and a joint communiqué on bilateral cooperation.
A joint media conference is planned before Hun Sen returns to Cambodia on Saturday afternoon.
This year marked the 65th anniversary of diplomatic relations between the two neighbours.