Bottom indexing dish radical — a pictograph of a footed bowl. It names what is being coveted in 盗: a vessel of food or treasure. Same dish family: 盘, 盆, 盖.
Top 次 originally pictured a person with mouth open and saliva at the side. In 盗 it carries that 'mouth watering with greed' image: the would-be thief eyes the goods and salivates. Semantic, not phonetic — it gives no sound to dào.
