The Khmer have been in the lower northeast of present-day Thailand even longer than the Thai. There are many Khmer ruins dating from the pre-Angkor and the Angkor periods in the three provinces and beyond, notably at Phanomrung (Buriram), still with concentrations of Khmer-speaking communities nearby.
The dialect of Khmer spoken in Cambodia across the north is very similar to the dialect in Thailand, though in Thailand many Thai words are also used. There is a dialect called "Northern Khmer" which is like a hybrid between Khmer and Thai.
Northern Khmer are mostly found in the lower northeast of Thailand, in the provinces of Buriram, Surin and Sisaket, which border Cambodia. They are also known as Thai-Khmer or Khmer-Surin. Northern Khmer speakers are also found in villages along the Thai-Cambodian border in Prachinburi province. There is also a smaller group of Northern Khmer who live in Cambodia.

The Northern Khmer are traditionally rice farmers, following the rhythm of the monsoon which can be notoriously fickle, with one village able to plant crops while another suffers drought. They are also skilled timber-cutters and house builders, and many Khmer women weave silk and cotton cloth during the dry season. Due to lack of ground water, only small-scale agriculture is possible, apart from raising cattle or buffaloes. Their food is distinctively Khmer with the popular somlor (soup) and liberal use of prohok.
Music is also very much part of their culture with the Khmer violin and pleng kantrum (Khmer folksong) at the center of village life and celebrations. They dress much like the Thai, but with distinctive colors and patterns in their sarongs.

Outwardly the Northern Khmer are followers of Theravada Buddhism, with a strong admixture of spirit-worship and divination. This is performed by the kruu, who may be either a monk or a layman. As well as Buddhist festivals, they also hold a festival to the spirits of the dead known as Prachum Ben. Most Khmer houses have a spirit shelf near the house, and another inside the house with items placed there by the khruu.

The Northern Khmer people need to be given the chance to hear the life-changing gospel so they can enjoy life to the full.

Pray for loving gospel workers to catch a vision for reaching the Northern Khmer people for Jesus and that in God's sovereign timing the hearts of these people would be open and ready to follow him.
Pray for Jesus movements to bless extended families so the gospel will spread rapidly.
Pray for the spiritual lives of the Northern Khmer people to become fruitful so others will be drawn to Jesus Christ.

Scripture Prayers for the Khmer, Northern in Cambodia.

https://joshuaproject.net/people_groups/19921/TH
https://en.wikipedia.org/wiki/Northern_Khmer_dialect
https://en.wikipedia.org/wiki/Northern_Khmer_people