Left side 朕 supplies the sound - zhèn drifting to téng through a zh/t alternation in old readings. 朕 is the imperial first-person pronoun used by emperors. Same phonetic feeds 滕, 誊, 藤. Indexed under Kangxi #130 肉 (ròu, meat) via the meat-radical ⺼ tucked inside 朕 on the left.
Three-stroke horse on the lower right, contributing the meaning. 腾 originally pictured a horse galloping fast, leaping into the air - bound forms 奔腾 to gallop, 飞腾 to soar, 腾飞 to take off all keep that surging-upward sense. Simplified 马 preserves the running silhouette of full-form 馬.
Filed under radical 肉 (ròu, #130) by convention. 肉 is not a separate component in 腾, so no strokes are highlighted.
