A tsakiyar tsakiyar zuwa ƙarshen karni na 19, Gwamnatin Burtaniya taIndiya ta sa ido sosai kan yadda ake kula da batutuwan Birtaniyya a cikin Lanna, musamman tare da madaidaicin iyakoki kusa da kogin Salween da ke shafar kasuwancin teak na Burtaniya.Yarjejeniyar Bowring da yarjejeniyoyin Chiangmai da suka biyo baya tsakanin Siam da Biritaniya sun yi ƙoƙarin magance waɗannan matsalolin amma ya ƙare a cikin tsoma bakin Siamese a cikin mulkin Lanna.Wannan tsangwama, yayin da aka yi niyya don ƙarfafa ikon Siam, ya sa dangantakar da ke tsakanin su da Lanna ta yi rauni, wanda ya ga ana lalata ikonsu na gargajiya.A ƙarshen karni na 19, a matsayin wani ɓangare na ƙoƙarin daidaita Siamese, an maye gurbin tsarin gudanarwa na gargajiya na Lanna a hankali.Tsarin Monthon Thesaphiban, wanda Yarima Damrong ya gabatar, ya canza Lanna daga jihar gamuwa zuwa yankin gudanarwa kai tsaye karkashin Siam.Har ila yau, wannan lokacin ya shaidi bunkasuwar }ungiyoyin Turai da ke fafutukar neman hakin katako, wanda ya kai ga kafa Sashen dazuzzuka na zamani da Siam ya yi, wanda ya kara rage cin gashin kai na Lanna.A shekara ta 1900, an haɗa Lanna bisa ƙa'ida zuwa cikin Siam a ƙarƙashin tsarin Monthon Phayap, wanda ke nuna ƙarshen ainihin siyasar Lanna.Shekarun da suka biyo baya sun shaida ƴan adawa ga manufofin daidaitawa, kamar Tawayen Shan na Phrae.Sarkin Chiang Mai na ƙarshe, Yarima Kaew Nawarat, ya yi aiki galibi a matsayin ɗan biki.An narkar da tsarin Monthon bayan juyin juya halin Siamese na 1932. Zuriyar sarakunan Lanna na zamani sun karɓi sunan "Na Chiangmai" bayan Dokar Sunan Sarki Vajiravudh ta 1912.