Htaccess Remove Index.php From A URL - wordpress

Question

I looked at this: htaccess remove index.php from url but it didn't work and in the comments there seems to be disagreement on the top answer.
If I type in http://www.example.com/thanksgiving/index.php/getThankyou I get the page I want served.
If I type in http://www.example.com/thanksgiving/getThankyou I get a 404.
What I've tried in my htaccess:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^/thanksgiving/(.*)/$ /thanksgiving/index.php/$1 [L]
</IfModule>
How do I do it so /thanksgiving/getThankyou/ or any url starting with /thanksgiving in the url leads to the proper resource being served? Again, it is currently available when index.php is in the url.
I also tried: RewriteRule ^/thanksgiving/[^/]*/$ /thanksgiving/index.php/$1 [L] but that didn't work either...
Edit: It seemed part of the htaccess is being set by wordpress and may be conflicting with the desired behavior above:
The wordpress part of the same htaccess is:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
Is this interfering? How do I reconcile this with the /thanksgiving/ urls which are not part of the Wordpress application?
Edit:
The above only pertains to the root (public_html) htaccess, below is the htaccess in /thanksgiving/ itself, please analyze for conflicts, thanks for all your help!
<IfModule mod_rewrite.c>
<IfModule mod_negotiation.c>
Options -MultiViews
</IfModule>
RewriteEngine On
RewriteBase /
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ /$1 [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
# Handle Authorization Header
RewriteCond %{HTTP:Authorization} .
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
</IfModule>
# Do not change this line.
# Change example.com to your domain name
RewriteCond %{HTTP_HOST} ^(www.)?example.com$
# Change your_app_name to the subfolder name
RewriteCond %{REQUEST_URI} !^/thanksgiving/
# Don't change the following two lines.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# Change your_app_name to the subfolder name
# Change example.com to your domain name
RewriteRule ^(.*)$ /thanksgiving/$1
RewriteCond %{HTTP_HOST} ^(www.)?example.com$
RewriteRule ^(/)?$ thanksgiving/index.php [L]

Answer 1

You need to remove the leading slash from your rewrite pattern :
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(?:thanksgiving/)?(.*)$ /thanksgiving/index.php/$1 [L]
</IfModule>
Otherwise the rule will accept the uri starting with a double leding slash (ie : //thanksgiving/ ) .