Well.., not quite. Khmer people are ancient race too just like Javanese and Malay Srivijayan. It was highly possible during the fall of Chenla kingdom, the land of Cambodia were fell under disunity and later, parts of it was conquered under Javanese domination. At that time Srivijaya-Sailendra were the formidable maritime navy force. It was mentioned in Cambodian chronicle about Java through their "Javaka (Zabaj) Legends".

What they meant by Java at that time probably refer to Sailendra-Srivijayan empire. At that time Javan Sailendra and Sumatran Srivijaya merge. The power was held by Sailendra kings and the center court shifted to Java. Possibly the princes of Chenlas were taken as royal hostage in Javan court of Sailendra. Educated and groomed to be the official ruling agent-vassal of Java. Jayavarman II, the founder of Cambodian Angkor period was stayed in Java in his early youthful years, probably he witnessed the construction of Borobudur. Later Samaratungga the Maharaja of Java send him back to Cambodia to rule on his behalf. However Jayavarman II break the allegiance vow and proclaimed himself as Devaraja of Kambuja.
Jayavarman II is widely regarded as the king that set the foundation of Angkor period in Cambodian history, began with the grandiose consecration ritual conducted by Jayavarman II (reign 790-850) in 802 on sacred Mount Mahendraparvata, now known as Phnom Kulen near Angkor, to celebrate the independence of Kambuja from Javanese dominion. At that ceremony Prince Jayavarman II was proclaimed a universal monarch (Kamraten jagad ta Raja in Cambodian) or God King (Deva Raja in Sanskrit). The word "Kamraten" derived from Raten is similar with Javanese title "Ratu" which means "ruler". According to some sources, Jayavarman II had resided for some time in Java during the reign of Sailendras, or "The Lords of Mountains", hence the concept of Devaraja or God King was ostensibly imported from Java. At that time, Sailendras allegedly ruled over Java, Sumatra, the Malay Peninsula and parts of Cambodia.
There is some speculations about Jayavarman II origin, was he a Khmer prince held as royal hostage in Java, or even he was a Javanese governor himself that proclaimed independence from central govt in Java. Another oppinion pointed out that the toponim Java was probably means Cham, not Java. However the established historian theories did link Cambodia with ancient Java during Sailendras rule.
The Philippines' Laguna copperplate inscription did mention about Mdaη (Medang kingdom) in Java. And the script here ar similar to Javanese script too... Suggested the ancient link between Indonesia and Philippines.
Srivijaya legacy in Indonesia
Palembang Srivijayan style Bride
Modern Indonesian nationalists have also invoked Srivijaya along with Majapahit, as a source of pride in Indonesia's past greatness. Srivijaya has become the focus of national pride and regional identity, especially for the people of Palembang, South Sumatra province, and the Malay people as a whole. For the people of Palembang, Srivijaya has also become a source of artistic inspiration for Gending Sriwijaya song and traditional dance, as well as the glittering gilded Srivijayan style Palembang bride costume.