I tend to use italics for thought as well, though anything I don't want Lili to catch wind of I'll simply narrate in thought rather than put in italics. (However, if you do see something in my narration you'd like for her to hear, just note me also and I can easily alter things ^^) Kiku's very much in his own head at times, so you might hear some interesting things~
Also, I do sometimes use italics to denote his 'conversations' with the plants. If you do run into one of those and it confuses you as to which are his thoughts and which are the plants' thoughts, just let me know ^^