How to disable the android wear back swipe?

There is an attribute in window style to disable this behavior:

<style name="AppTheme" parent="@android:style/Theme.DeviceDefault.Light">
    <item name="android:windowSwipeToDismiss">false</item>
</style>

Once you disable it you have to provide other way of exiting your app.
There is a DismissOverlayView class (listed here https://developer.android.com/training/wearables/apps/layouts.html#UiLibrary) that you should use instead.
Basically it provides an overlay that will show a red button with cross after a long press. Clicking the red button will exit your app.

Here is a video from Google I/O 2014 with some bookmarked moments:
https://www.youtube.com/watch?v=sha_w3_5c2c#t=1390 <- disabling android:windowSwipeToDismiss
https://www.youtube.com/watch?v=sha_w3_5c2c#t=1505 <- Java code for DismissOverlayView

You can also check another video called:
Fullscreen apps for Android Wear:
https://www.youtube.com/watch?v=naf_WbtFAlY

You can try to write AndroidManifest.xml theme

android:theme="@style/Theme.Wearable.Modal inside activity tag

<activity
            android:name="com.smart.remote.wear.MainActivity"
            android:label="@string/app_name"
            android:theme="@style/Theme.Wearable.Modal">