The Southern League Division One outfit were expected to win the contest, but they certainly put their non-league opponents to the sword.
Thane led the way with 151 not out, while Willcock finished unbeaten on 108, as they shared an unbroken second-wicket stand of 260.
Jordan Hobday (22) was the only man out, with the score on 51.
In reply, RNA, chasing more than 15 an over to win, were bowled out for 96 as Hook won the game by 217 runs.
The victory booked them a place in the last eight of the competition and Hook and Newnham Basics B will hope to do the same on Monday night. However, they face a tough task as they take on Odiham and Greywell at May’s Bounty.
Hook will hope to maintain their 20-over form on Sunday, when they play their Southern Electric t20 Plate match at their home ground, King George V Playing Fields.
It is set to be a great day for all the family with a barbecue and bar open – as well as a double bill of t20 games taking place.
The opening match will see Sparsholt and St Cross battle it out from 12.30pm.
The winners will then take on Hook at 4pm.
Hook captain Matt Love said: “We are really looking forward to Sunday and want to make it a really fun day for all the family.”
Before Hook focus on the t20 competition, they are in Southern League Division One action with a trip to title-chasing Sarisbury Athletic on Saturday.
The south Hampshire side come into the game after a victory against Basingstoke at May’s Bounty, which was their sixth straight win.
Last weekend, Hook lost by one wicket at leaders New Milton, as the home side maintained their 100 per cent record.
The visitors, put into bat, were bowled out for 125, the second highest total New Milton had conceded this season, as Thane (50) and Matt Buckingham (32) top scored.
The home side looked to be cruising to victory at 100-3, but then top scorer Nick Park (39) was dismissed by Kevin Poulter (3-24).
New Milton’s Nick Elliott (32) took up the mantle and got his side one run from victory before falling to Shane Brewer (3-15) making the score 124-7.
The Hook bowler struck again next ball as he bowled Ashley Collison and a single saw the game tied with the home side having two wickets left.
This became one as Dan Loader was caught behind by Josh Buckingham, but New Milton got over the finishing line to win by one wicket.
Love said: “We bowled superbly again and I was really pleased with the attitude as we never gave up.
“It is frustrating at the moment in the league as we know that if we can get our batting going we will be a match for anyone.”