I found i had to leave the departure date blank otherwise it thought arrival/departure were the same day and that meant you were in transit, not staying in Thailand. Site logic is bad. Couldn't enter the accomadation data until i dropped the departure date. Note, i was trying to do this enroute from USA so guessing the dateline had something to do with it...
Note 2, remember to print and keep the document, you might need it is you apply for an extension of fire s be visa in country...
If your insurance expires before your visa, you've not met the visa requirements and you will be on overstay from that time on. Suggest you make appropriate adjustments. To don't want overstay on your record.