Yaƙin Burma –Siamese (1547 – 1549), wanda kuma aka fi sani da Yaƙin Shwehti, shine yaƙin farko da aka gwabza tsakanin daular Toungoo na Burma da Masarautar Ayutthaya ta Siam, kuma farkon yaƙe-yaƙe na Burma – Siamese wanda zai ci gaba har zuwa tsakiyar karni na 19.Yakin ya yi fice wajen shigar da yakin zamani na farko a yankin.Har ila yau, abu ne sananne a tarihin Thai ga mutuwar a yakin Sarauniyar Siamese Suriyothai a kan giwarta na yaki;Ana yawan kiran rikicin a Tailandia a matsayin yakin da ya kai ga asarar Sarauniya Suriyothai.An bayyana casus belli a matsayin wani yunƙuri na Burma na faɗaɗa yankinsu zuwa gabas bayan rikicin siyasa a Ayutthaya ^[41] da kuma yunƙurin dakatar da kutse na Siamese a gabar Tenasserim na sama.^[42] Yaƙin, a cewar Burma, ya fara ne a cikin Janairu 1547 lokacin da sojojin Siamese suka mamaye garin Tavoy (Dawei).Daga baya a cikin shekarar, sojojin Burma karkashin jagorancin Janar Saw Lagun Ein sun sake kwace gabar Tenasserim ta Upper zuwa Tavoy.A shekara ta gaba, a cikin Oktoba 1548, sojojin Burma uku karkashin jagorancin Sarki Tabinshwehti da mataimakinsa Bayinnaung sun mamaye Siam ta hanyar Pagodas Uku.Dakarun Burma sun kutsa har zuwa babban birnin kasar Ayutthaya amma sun kasa kwace birnin mai kagara.Wata daya a cikin kewayen, hare-haren ramuwar gayya na Siamese sun karya shingen, suka kori sojojin mamaya.Amma Burma sun yi shawarwarin zaman lafiya don musanya dawowar wasu manyan sarakunan Siamese guda biyu (magaji Yarima Ramesuan, da Yarima Thammaracha na Phitsanulok) da suka kama.