Title: Tridu Songtsen
Content:  Tridu Songtsen, Tridu Songtsen or Dusong Mangban, (b.668 – 704d.; r. 676–704 CE) was an emperor of the Tibetan Empire from 676 to 704.
Title: 704
Content: Emperor Tridu Songtsen dies in battle and is succeeded by his mother Khri ma lod who becomes de facto ruler of the Tibetan Empire. She begins a massive expansion into the Tarim Basin and Northern China. 
Title: Tridu Songtsen
Content:  'Dus-srong he married two women from important Tibetan clans — 'Dam-gyi Cog-ro-bza', and Chimza Tsunmotog (Wylie: mChims-bza' bTsan-ma Thog-thog-sten), Princess of Chim, with whom he had a son Khri-lde-gtsug-btsan (also known later as Mes-ag-thoms) in 704. It seems 'Dus-rong also had a Turkish bride, as the Tibetan Annals record the death of the princess "Gatun" (= Turk: Khatun?) in 708.
Title: Tridu Songtsen
Content:  'Dus-srong died in 704 in battle in Mywa territory in modern Yunnan. The Tang Annals state he was on his way to suppress tributary kingdoms on the southern borders of Tibet, including Nepal and parts of India. There was a dispute among his sons but, "after a long time" the people put seven year old Qilisuzan, later known as Me Agtsom, on the throne. 'Dus-srong is buried next to his father in the Royal Burial grounds near Yarlung.
Title: Tridu Songtsen
Content:  'Dus-rong ascended the Tibetan throne after the death of his father, Mangsong Mangtsen, in 676. The Old Book of Tang says that 'Dus-srong was eight years old in 679 — nine years old by Western reckoning. He was, therefore, presumably born in 670 and was six or seven years old when he began his reign. Due to his youth, he was enthroned with the minister Gar Tongtsen's second son, Khri 'bring, to act as regent.
Title: Tridu Songtsen
Content:  699 he pretended to organise a great hunt and then had his men turn on members of the mGar and their supporters. Then he personally marched north and confronted Gar Trinring Tsendro, who surrendered without a fight and, according to the Old Book of Tang, committed suicide. His brother fled to China. After this, 'Dus-srong asserted the right of the power of the king over his ministers. 'Dus-srong personally led 10,000 troops into four battles in some unnamed place to the northeast in 702. The next year he "established his authority over the 'Jang (Nanzhao), he imposed tribute on the White Mywa, he subdued the Black Mywa (probably the Miao people), and so on."
Title: Mé Aktsom
Content:  It is very unclear, however, from the sources exactly what happened after the death of Tridu Songtsen. According to the Tibetan Annals, "he who would be crowned king" (i.e. Mes-ag-tshoms?) was born in the spring of 704, just a few months before his father died. Beckwith states that in the winter of 704–705, Lha ("Balpho" or Lha Balpo), one of the sons of Tridu Songtsen, took the throne, but Thrimalö, the empress dowager, wife of the second emperor, Mangsong Mangtsen, and mother of Tridu Songtsen, "dethroned Lha in favor of the infant Rgyal Gtsug ru, the future Khri gtsug brtsan, popularly known as Mes ag tshoms. Revolts and executions accompanied the virtual coup, but the Annals and Chinese sources have little to report on them. Lha apparently was not killed, but only forced into semiretirement. It was thus, perhaps, the "Retired Emperor" Lha who actually received and married the Chinese princess Chin-ch'eng in 710. In any event, Tibet experienced more internal unrest, and was conspicuously quiet on its borders with China." Whatever the case, Mé Aktsom was crowned king in 705 CE, although he was not formally enthroned until the death of Thrimalö in 712.
Title: List of regents
Content: Khri ma lod for her son Tridu Songtsen (675–689) and again for her grandson Me Agtsom (704–712) 
Title: Tridu Songtsen
Content:  Although 'Dus-srong is primarily remembered as a warrior, according to the Testament of Ba, he supported Buddhism and had a temple called Khri rtse built in Gling Khams, "and so on", which is recorded on an inscription at sKarchung written by Emperor Sadnalegs about a century later.
Title: Khri ma lod
Content:  Khri ma lod was married to emperor Mangsong Mangtsen (Trimang Löntsen' or Khri-mang-slon-rtsan). The emperor died in the winter of 676-677, and in the same year she gave birth to the emperor's son Tridu Songtsen (Khri 'dus-srong btsan or Khri-'dus-srong-rtsan). The Zhangzhung revolted early in her son's reign. She shared power with the Gar (Mgar) clan. When her son Tridu campaigned in the northeast 700-4 CE, she resumed her administrative regency at home. Khri ma lod's grandson Gyältsugru (Rgyal-gtsug-ru) was born in 704 to her daughter-in-law Chimza Tsunmotog (mChims-bza' bTsan-ma Thog-thog-sten), Princess of Chim. Upon the death of Tridu Songtsen that year, his elder son Lha Balpo (Lha Bal-pho) briefly succeeded him before Khri ma lod dethroned him at Pong Lag-rang in favor of the infant Gyältsugru. Khri ma lod had arranged for a royal marriage of Gyältsugru to a Chinese princess. The Princess Jincheng (金城公主, Tibetan: Kyimshang Kongjo) arrived in 710, but it is somewhat unclear whether she married the seven-year-old Gyältsugru or the deposed Lha Balpo. Khri ma lod died in 712. Gyältsugru was then officially enthroned with the royal name Tride Tsuktsän. Khri ma lod remains the only woman in Tibetan history to rule Tibet.

Question: Who is the mother of Tridu Songtsen?
Answer: Khri ma lod.
Thrimalö.